Methods for manufacture of composite articles having an empty space, wherein the empty space's cross section measure is greater than any open part's cross section of the article for withdrawal of an inner male tool, are known. That is, the use of a lost core mould or a collapsible male tool body, for forming such empty space, is well known within the art. Lost core moulding methods are also used for making curved hollow beams where withdrawal of a rigid male tool from the empty space is impossible without breaking the final article.
Rigid interior mould inserts are used in the form of several connectable units for removing the mould inserts from the final article. The complexity of connecting these units together, and the occupied interior of the blank material during the curing procedure, will imply an expensive production performance.
WO 03/064130 discloses a mould insert produced of a particulate material in a gas-tight bag giving the mould insert the desired exterior shape while the bag is vacuum sealed such that the particulate material forms a body of firm cohesion. The composite material, such as prepreg material, is formed around the mould insert and after the curing of the composite material the gas tight bag is punctured, whereupon the cohesion of the mould insert collapses when the vacuum is ruptured. The particulate material is removed together with the bag material from the final article.
Also GB 2284173 discloses an inner core tool for a lost core moulding process. The inner core tool is made by a bag with particles which will rigidify when evacuating air from the bag interior. The inner core tool is inserted in a rigid mould establishing a pressurisible plenum volume conforming the form of the finished article. A polymerisable material is introduced into said volume.
The inner core tool is removed after polymerization of the article.
However, there still exists a problem how to reduce the production time for producing hollow articles, e.g made of plastic, using a vacuum sealed bag with particulate material as a collapsible inner shape tool or core tool. Also, there is a need of controlling the curing cycle of the article to be produced.
The object of the present invention is to overcome the drawbacks of known methods and achieve further development of the method disclosed in WO 03/064130, which document however discloses a well working method.